The present invention relates to hair coloring and, in particular, it concerns determining a hair color treatment for hair including previously dyed hair.
By way of introduction, different hair samples react differently to the process of bleaching and dyeing due to, amongst other factors, the different chemical pigment structure of the hair as well as the condition of the hair to be treated. The prior art includes many methods which try to predict final hair color in order to minimize error and increase customer satisfaction with the hair color products.
Of relevance to the present invention is U.S. Pat. No. 4,434,467 to Scott. The patent to Scott describes a method whereby the customer chooses a color from a database that is the closest match to his or her own hair color. The customer then chooses a desired final color from the database. The computer then suggests a treatment based on the manufacturer instructions. A shortcoming of the aforementioned system is that the customer has to determine by visual comparison, the closest match to his or her own hair color. A further shortcoming of the aforementioned system is that the system is limited to hair treatments, which are based upon a fixed and limited selection of initial hair colors, thereby not taking into account the individual's hair color.
Also of relevance to the present invention is U.S. Pat. No. 5,609,484 to Hawiuk. Hawuik teaches the use of color filament swatches to recreate the initial hair color and then to add color filament swatches, which are related to a known hair dye, to see how the initial hair color is affected by the hair dye. A shortcoming of the aforementioned system is that the system is not accurate. A further shortcoming of the aforementioned system is that determining the initial color involves a high degree of estimation. An additional shortcoming of the aforementioned system is that this system does not address bleaching of the initial hair color.
Of most relevance to the present invention is U.S. Pat. Nos. 6,067,504, 6,157,445, 6,308,088, 6,314,372 and 6,330,341 to MacFarlane, et el. These patents discuss a method, which first includes obtaining a reflectance spectrum from a sample of hair. The coefficients of the Hunter L, a and b color coordinates of the reflectance spectrum of the hair sample are then analyzed by a computer. The initial hair color is then classified by the computer according to a range of coefficients of the color coordinates stored in a lookup table. A user then chooses a desired hair color from a choice of possible final colors. The computer then determines the appropriate hair treatment based upon a hair treatment stored in a lookup table for the initial hair color and the desired final hair color. A shortcoming of the aforementioned system is due to the initial hair color being classified according to an artificial color, which fits into a range of possible colors. Therefore, the suggested hair treatment does not accurately reflect the users initial hair color. A further shortcoming of the aforementioned system is that the creation and maintenance of the hair treatment lookup table requires a vast number of experiments. For example, for each hair dye, experiments are needed for all the possible initial and final hair colors that can be achieved for that dye.
Also of relevance to the present invention is U.S. Pat. No. 6,707,929 to Marapane, et al. Marapane, et al. teaches calculating final color coordinates (such as L, a, b or RGB) of hair by using equations which define the relationship between the untreated hair color coordinates and the treated hair color coordinates for a particular dye. This method overcomes some of the shortcomings of the MacFarlane, et al. patents. Nevertheless, all the above methods (including Marapane, et al.) use a color coordinate system, such as L, a, b, or RGB. Color coordinates can be misleading in certain cases. For example, two samples of hair, which look substantially the same to the human eye may have the same L, a, b color coordinate values even though they have different spectra of reflectance, and therefore, different concentrations of components. For example, one natural blond hair sample which is colored with dye A, may have the same color coordinates as another hair sample, say, a brown hair colored with a dye B. Moreover, a large number of hair samples, each having different reflectance spectra, may all generate the same or very similar color coordinates especially as the cuticles and white envelope of the hair also contribute to the reflectance spectrum. However, the same hair treatment applied to these hair samples will generate different final hair colors due to different initial concentrations of each of their components. Therefore, simply looking at the L, a, b color coordinates or other color coordinates may lead to spurious results.
Moreover, none of the abovementioned methods models the color treatment process based on the chemical properties of hair.
Mixing hair dyes is used widely at hair salons in order to help a customer obtain a desired hair color that a single hair dye cannot give. None of the abovementioned methods predicts the final color of hair that is colored with a mixture of two or more hair dyes without the need to perform experiments on specific combinations of dyes. In other words, all the above mentioned methods require coloring a large quantity of different hair samples with every possible mixture and building a model for each mixture separately. Therefore, it is not feasible with the prior art to cover all possible color mixtures in order to provide a global solution to this problem.
Also, the prior art methods do not effectively address coloring previously dyed hair.
There is therefore a need for a hair color determination system and method for accurately determining a suitable hair color treatment for all types of hair including natural hair as well as previously dyed and/or bleached hair and including using a mixture of two or more dyes.